(1) Field of the Invention
The present invention pertains to a connection board that is mounted in a terminal box of a three phase, dual voltage electric motor. The unique construction of the connection board enables electric terminals on the board to be connected to the lead wires of the three phase electric motor in both low voltage and high voltage applications of the motor. In both applications of the motor the connection board provides three electric terminals for connection with separate power supply wires that are easily accessible by the end user of the motor for connection of the power supply wires to the terminals.
(2) Description of the Related Art
In the majority of three phase electric motors manufactured, and in particular for those electric motors manufactured for assembly into home appliances, the motor is manufactured with a terminal box mounted to the motor frame or exterior shell. The terminal box houses the ends of the motor wiring leads that are accessible in the terminal box by removing a cover plate of the terminal box. The end user, for example the appliance manufacturer, would remove the cover plate to connect the appliance wiring to the wiring leads of the electric motor. For example, in a three phase electric motor, three power supply wires of the appliance would be connected with the lead wires of the electric motor. The motor would typically have nine numbered lead wires for a motor without a thermal protector or twelve numbered lead wires for a motor having a thermal protector.
These designs of electric motors, where the power supply wires and the motor lead wires are connected in the terminal box, are typically referred to as “loose-lead” constructions, i.e. there is no connection board or separate mechanism employed for connecting the power supply wires with the motor lead wires. In loose-lead constructions, the end user connects the three incoming power supply leads directly to the motor lead wires by twisting together ends of the wires from which their insulation has been stripped and attaching twist-on connectors on the twisted wire ends. However, this method of securing together the ends of the motor lead wires and the power supply wires in cumbersome. This is particularly true with dual voltage electric motors which have nine to twelve numbered lead wires within the terminal box that much be properly connected with each of the three power supply wires to provide the proper voltage to the motor and for proper rotation of the motor. With their being so many lead wires present in the terminal box, the manual twisting together of the lead wire ends and their being secured together by the twist-on connectors would often cause misconnections between the wires. This would result in motor failures when high voltage would be applied to a low voltage wired motor.
To overcome the problems associated with connecting the wires of three phase, dual voltage motors, connection boards were employed to organize the wire connections. With there being nine to twelve motor lead wires extending from a three phase, dual voltage motor, the prior art connection boards would employ twelve dual-flag type connection points on one side of the connection board that would be accessible by the end user in the motor terminal box. Although connections to the dual-flag type connection points were more convenient than the twist-on connections of the prior art, all of the nine to twelve motor lead wires and the three power supply wires would be connected to the top or exterior surface of the connection board inside the terminal box. The presence of so many lead wires on the exterior surface of the connection board made it difficult to understand which lead wires were to be interchanged when a voltage change of the motor was needed, i.e. from low voltage to high voltage or from high voltage to low voltage. With the prior art connection board having only dual-flag type connection points, it was necessary for the motor end user to supply flag terminals on the power lead wires leading into the motor terminal box instead of utilizing the bare solid strand wire commonly used.
Terminal blocks have also been employed in an effort to simplify the connections of the many motor lead wires of three phase, dual voltage motors. The terminal blocks would be mounted in the terminal boxes of the motors with six to nine threaded stud and nut terminals on the terminal block being accessible in the terminal box. The threaded stud and nut terminals were provided for wiring both the motor lead wires and the power supply wires together. Use of the threaded stud and nut terminals for connecting the wires required that each wire have an eyelet type connector. However, the prior art terminal blocks also have their disadvantages. When the particular motor was provided with a thermal overload protector device, the motor would have twelve lead wires which would require a larger nine post terminal block. The larger nine post terminal block would also require a larger terminal box on the motor to house the larger terminal block. To change over the voltage of the motor additional shorting bars were required. The shorting bars were connected, post to post, to change the voltage of the motor. Changing the positions of the shorting bars would require removing the nuts from the threaded studs to which the bars were connected and from the threaded studs to which the bars would be connected in making the voltage change. Again, making voltage changes in this manner was very cumbersome to the end user of the motor.
In mounting the prior art connection board or terminal block to the interior of the motor terminal box, at least two non-captive screws would be employed. In addition, a number of spacers corresponding to the number of screws were also employed. The spacers would support the connection board or terminal block in a spaced position from the back wall of the terminal box to accommodate the lengths of motor lead wires between the connection board or terminal block and the back wall of the terminal box. However, because the mounting screws and their spacers were non-captive or not integrally attached to the connection board or terminal block, assembling the mounting screws and spacers to the connection board or terminal block and then attaching the board or block to the interior of the terminal box was difficult to assemble by the end user due to the numerous component parts needing alignment. In addition, attaching the spacers to the connection board or terminal block and to the back wall of the terminal box also presented the potential for damaging the motor lead wires by crimping the wires between the spacers and the connection board or terminal block or between the spacers and the terminal box back wall when assembling the connection board or terminal block to the terminal box.
What is needed to overcome these problems of the prior art is a connection board that is designed for use with three phase, dual voltage electric motors that organizes the connections of the motor lead wires on an exterior surface of the connection board that is accessible by the end user, that positions the electric terminals of the motor lead wires in an arrangement that facilitates the conversion of the motor lead wires between low voltage and high voltage connections and that simplifies the connection of the three separate power supply wires to the wiring of the electric motor.